An electrostatic power generator and an electrostatic actuator each comprising an electret film are disclosed in Japanese Patent Laying-Open Nos. 2006-180450 and 4-112683 respectively, in general.
This electrostatic power generator disclosed in Japanese Patent Laying-Open No. 2006-180450 is constituted by two substrates provided to be opposed to each other at a prescribed distance therebetween. A plurality of strip-shaped electrodes are formed on a surface, opposed to the second substrate, of the first substrate. A plurality of strip-shaped conductive layers are formed on a surface, opposed to the first substrate, of the second substrate, and an electret film made of a charge holding material is formed on this conductive layers. In this electrostatic power generator, at least one of the two substrates repeatedly vibrates by receiving inertial force, whereby charges induced in the electrodes opposed to the electret film are changed due to charges stored in the electret film and hence the changed charges are output as a current.
The electrostatic actuator disclosed in Japanese Patent Laying-Open No. 4-112683 is constituted by a stator including a plurality of electrodes and a vibrator including a substrate made of Teflon (registered trademark). A prescribed region of this substrate made of Teflon (registered trademark) is partially made as an electret by corona discharge. More specifically, one region, made as the electret, of the substrate made of Teflon (registered trademark) is in the form of a strip and a plurality of strip-shaped regions made as the electrets are formed on the substrate at constant intervals. The plurality of electrodes included in the stator and the plurality of regions, made as the electrets, of the substrate made of Teflon (registered trademark) are arranged to be opposed to each other, and the potentials of these plurality of electrodes are changed (a positive voltage, 0 and a negative voltage), whereby the vibrator included in the substrate made of Teflon (registered trademark) is moved in a horizontal direction with respect to the opposed stator.
In the electrostatic power generator disclosed in Japanese Patent Laying-Open No. 2006-180450, however, the electret film made of the charge holding material is formed in the form of a strip and there is a problem that charges flow out of the ends of the strip-shaped electret film. Thus, the quantity of charges stored in the electret film is reduced, and hence the quantity of power generated in the electrostatic power generator is reduced.
In the electrostatic actuator disclosed in Japanese Patent Laying-Open No. 4-112683, there is a problem that charges flow out of the plurality of regions, made as the electrets, of the substrate made of Teflon (registered trademark) to regions not made as the electrets. Thus, difference between the potential of each region not made as the electret and the potential of each region made as the electret is reduced, and hence a moving operation and a stop operation of the vibrator are slowly switched. This substrate of Teflon (registered trademark) partially made as the electret which is disclosed in Japanese Patent Laying-Open No. 4-112683 is conceivably employed as the second substrate of the electrostatic power generator disclosed in Japanese Patent Laying-Open No. 2006-180450. In this case, however, difference between the potential of each region made as the electret and the potential of each region not made as the electret is reduced, whereby the changed quantity of charges induced in the electrodes opposed to the substrate made of Teflon (registered trademark) is reduced and hence the quantity of power generated in the electrostatic power generator is reduced.